Rapier looms are widely used nowadays because the weft yarns are efficiently guided within the shed, thanks to a bringer rapier head clamp and a taker rapier head clamp which cooperate in a central zone of the shed in order to transfer a weft yarn from the bringer rapier to the taker rapier. Rapiers are formed of a head, provided with weft yarn clamping means, and a driving member, such as a rod or a belt, which moves the head within the shed, during weaving of a fabric. The driving member usually cooperates with a pinion located on one side of the fabric. Once a pick, the shed is opened and a reed is moved in a backward position, so that the shed and the reed together define a kind of a corridor into which the two rapiers travel up to the middle of the fabric.
In order to allow an efficient transfer of the weft yarn from the bringer rapier to the taker rapier, the rapiers must exactly meet in the middle of the shed. The rapier heads can be considered to be guided by the warp yarns since the transverse section of the corridor is close to the transverse shape of the rapier heads. However, frictions on the warp yarns are damageable and may cut some warp yarns and lead to faults in the fabric. If the rapier heads are not efficiently guided by the warp yarns, they tend to “shake” within the shed because of the dynamic deformation of the driving member, so that their respective positions, when they arrive at the take-over region, are uncertain.
DE-A-10 2006 030 628 discloses a reed with dents made of a magnetic material.
EP-A-1 479 808 discloses a rapier device for a weaving machine where one rapier is provided with a permanent magnet in order to generate, in the take-over zone, a magnetic attractive force between the rapiers. This magnetic attractive force is active only in take-over zone, which does not prevent the rapiers to shake within the shed on their way towards this zone, to the point that they can be offset from each other when they reach this zone. In other words, the magnet may not be sufficient to guarantee that the rapier heads are correctly aligned in the take-over zone.
These inconvenients become more and more critical on large weaving machines where fabrics are woven on a width larger than four meters, e.g. five meters.
Similar inconvenients occur with weft yarns insertion systems which include only one rapier, either a bringer rapier or a taker rapier, which must be prevented from shaking when it travels within the shed.